PubMed Health⌕ Search

Biomedical subjects

L Simonsen

Publications and source records attributed to L Simonsen.

At least 55 records · Page 3Linked to original sources
PubMed1998

Pandemic versus epidemic influenza mortality: a pattern of changing age distribution.

Almost all deaths related to current influenza epidemics occur among the elderly. However, mortality was greatest among the young during the 1918-1919 pandemic. This study compared the age distribution of influenza-related deaths in the United States during this century's three influenza A pandemics with that of the following epidemics. Half of influenza-related deaths during the 1968-1969 influenza A (H3N2) pandemic and large proportions of influenza-related deaths during the 1957-1958 influenza A (H2N2) and the 1918-1919 influenza A (H1N1) pandemics occurred among persons <65 years old. However, this group accounted for decrementally smaller proportions of deaths during the first decade following each pandemic. A model suggested that this mortality pattern may be explained by selective acquisition of protection against fatal illness among younger persons. The large proportion of influenza-related deaths during each pandemic and the following decade among persons <65 years old should be considered in planning for pandemics.

Adolescent↗
PubMed1998

Dietary structured triacylglycerols containing docosahexaenoic acid given from birth affect visual and auditory performance and tissue fatty acid profiles of rats.

To examine whether it is possible to enhance the level of 22:6(n-3) in the central nervous system, newborn rats were fed dietary supplements containing oils with either specific or random triacylglycerol structure, but similar concentrations of polyunsaturated fatty acids. In the specific structured oil, 22:6(n-3) was located in the sn-2 position, whereas it was equally distributed among the three positions in the triacylglycerol molecule in the randomized oil. A reference group was fed rat milk before weaning and nonpurified diet after weaning. After 12 wk, the levels of 22:6(n-3) in brain and liver phospholipids were higher in the groups fed the experimental diets than in the reference group. The specific structured oil resulted in the highest level of 22:6(n-3) in the brain, whereas the level of 22:6(n-3) was highest in the liver of the group fed randomized oil, indicating differences in metabolism of fatty acids resulting from their position in the dietary triacylglycerol molecule. The higher levels of 22:6(n-3) were accompanied by significantly lower levels of the long-chain (n-6) polyunsaturated fatty acids compared with the reference group. The fatty acid profiles, including the level of 22:6(n-3), in the retina phospholipids were not affected by the three different diets apart from a lower level of 20:4(n-6) in rats fed the experimental diets, indicating a strong tendency to maintain a high level of 22:6(n-3) in the retina. The changes in the fatty acid profiles did not result in differences in learning ability, but caused changes in visual function, evidenced by higher latency of the b-wave and lower oscillatory potential, and in auditory brainstem response, evidenced by generally greater amplitude of wave Ia in the group fed specific structured oil.

Adipose Tissue↗
PubMed1998

Resistance to antimicrobial chemotherapy: a prescription for research and action.

The growing problem of resistance to antimicrobial chemotherapy was discussed by participants at the February 1995 workshop at Emory University on population biology, evolution, and control of infectious diseases. They discussed the nature and source of this problem and identified areas of research in which information is lacking for the development of programs to control of the emergence and spread of resistant bacteria. Particular attention was given to theoretical (mathematical modeling) and empirical studies of the within and between-host population biology (epidemiology) and the evolution of microbial resistance to chemotherapeutic agents. Suggestions were made about the kinds of models and data needed, and the procedures that could be employed to stem the ascent and dissemination of resistant bacteria. This article summarizes the observations and recommendations made at the 1995 meeting and in the correspondence between participants that followed. It concludes with an update on the theoretical and empirical research on the between- and within-host population biology and evolution of resistance to antimicrobial chemotherapy most of which has been done since that meeting.

Bacteria↗
PubMed1997

Influenza surveillance--United States, 1992-93 and 1993-94.

PROBLEM/CONDITION: CDC conducts active surveillance annually from October through May on the emergence and spread of influenza virus variants and the impact of influenza-related morbidity and mortality. Influenza activity is also monitored throughout the year by passive surveillance. REPORTING PERIOD COVERED: This report summarizes U.S. influenza surveillance from October 1992 through May 1994. DESCRIPTION OF SYSTEM: Influenza surveillance comprises four components, three of which provide weekly data from October through May: a) state and territorial epidemiologists provide estimates of local influenza activity; b) approximately 140 sentinel physicians report their total number of patient visits and the number of cases of influenza-like illness; and c) approximately 70 collaborating laboratories of the World Health Organization (WHO) report weekly influenza virus isolations and submit selected influenza isolates to CDC for antigenic analysis. Throughout the year, vital statistics offices of 121 cities report deaths related to pneumonia and influenza (P&I), providing an index of the impact of influenza on mortality. RESULTS: Influenza B viruses predominated during the 1992-93 influenza season, but influenza A(H3N2) isolates increased and were associated with outbreaks in nursing homes at the end of the season. The increase in influenza A(H3N2) activity was associated with a rise in P&I-related mortality. Preseason outbreaks of influenza A(H3N2) virus were reported during August and September 1993 in Louisiana. In the past, preseason outbreaks of influenza have been associated with earlier than usual epidemic-level activity. During the 1993-94 influenza season, activity rose during November and December and peaked earlier than usual, during the last week of December and the first week of January; influenza A(H3N2) viruses predominated. INTERPRETATION: The change in predominance from influenza B to influenza A in the spring of 1993 emphasizes the importance of annual influenza surveillance. Although influenza vaccine is effective against both influenza A and B, the antiviral drugs amantadine and rimantadine are effective only against influenza A. Outbreaks during the summer of 1993 emphasize that influenza should be considered a possible cause of respiratory infections during summer and early autumn. ACTIONS TAKEN: Surveillance data were provided weekly throughout the influenza season to public health officials, WHO, and health-care providers.

Humans↗
PubMed1997

The population genetics of antibiotic resistance.

Mathematical models are used to ascertain the relationship between the incidence of antibiotic treatment and the frequency of resistant bacteria in the commensal flora of human hosts, as well as the rates at which these frequencies would decline following a cessation of antibiotic use. Recent studies of the population biology of plasmid-encoded and chromosomal antibiotic resistance are reviewed for estimates of the parameters of these models and to evaluate other factors contributing to the fate of antibiotic-resistant bacteria in human hosts. The implications of these theoretical and empirical results to the future of antibacterial chemotherapy are discussed.

Anti-Bacterial Agents↗
PubMed1997

A method for timely assessment of influenza-associated mortality in the United States.

Influenza-associated mortality has traditionally been estimated as the excess mortality above a baseline of deaths during influenza epidemic periods. Excess mortality estimates are not timely, because national vital statistics data become available after a period of 2-3 years. To develop a method for timely reporting, we used the 121 Cities Surveillance System (121 Cities), maintained at the Centers for Disease Control and Prevention, as an alternative data source. We fit a cyclical regression model to time series of weekly 121 Cities pneumonia and influenza deaths for 1972-1996 to estimate the excess pneumonia and influenza mortality and to compare these figures with national vital statistics estimates for 20 influenza seasons during 1972-1992. Seasonal excess mortality based on 121 Cities correlated well with the national data: for 18 (90%) of 20 seasons, our influenza epidemic severity index category approximated the result based on national vital statistics. We generated preliminary severity categories for the four recent seasons during 1992-1996. We conclude that the 121 Cities Surveillance System can be used for the timely assessment of the severity of future influenza epidemics and pandemics. Timely pneumonia and influenza mortality reporting systems established in sentinel countries worldwide would help alert public health officials and allow prompt prevention and intervention strategies during future influenza epidemics and pandemics.

Centers for Disease Control and Prevention, U.S.↗
PubMed1997

The impact of influenza epidemics on mortality: introducing a severity index.

OBJECTIVES: The purpose of this study was to assess the impact of recent influenza epidemics on mortality in the United States and to develop an index for comparing the severity of individual epidemics. METHODS: A cyclical regression model was applied to weekly national vital statistics from 1972 through 1992 to estimate excesses in pneumonia and influenza mortality and all-cause mortality for each influenza season. Each season was categorized on the basis of increments of 2000 pneumonia and influenza excess deaths, and each of these severity categories was correlated with a range of all-cause excess mortality. RESULTS: Each of the 20 influenza seasons studied was associated with an average of 5600 pneumonia and influenza excess deaths (range, 0-11,800) and 21,300 all-cause excess deaths (range, 0-47,200). Most influenza A(H3N2) seasons fell into severity categories 4 to 6 (23,000-45,000 all-cause excess deaths), whereas most A(H1N1) and B seasons were ranked in categories 1 to 3 (0-23,000 such deaths). CONCLUSIONS: From 1972 through 1992, influenza epidemics accounted for a total of 426,000 deaths in the United States, many times more than those associated with recent pandemics. The influenza epidemic severity index was useful for categorizing severity and provided improved seasonal estimates of the total number of influenza-related deaths.

Cause of Death↗
PubMed1997

Long-lasting neurobehavioral effects of prenatal exposure to xylene in rats.

The persistence of neurobehavioral effects in female rats (Mol:WIST) exposed to 500 ppm technical xylene (dimethylbenzene, CAS-no 1330-20-7) for 6 hours per day on days 7-20 of prenatal development was studied. The dose level was selected so as not to induce maternal toxicity or decreased viability of offspring. Investigations of learning and memory abilities were performed using a Morris water maze. This task requires rats to spatially navigate, using distal extramaze cues to locate a small platform under the surface of the water in a large pool. At the age of 16 weeks, the exposed offspring showed impairments when the platform was relocated in the pool. Impaired performances after platform relocation were also observed in exposed offspring at 28 and 55 weeks of age, although the difference was not statistically significant at 55 weeks. These data could indicate that the effect was partly reversible, although over a long time period. However, another explanation could be that the animals became more practised at solving the problem (finding the platform) as continued testing occurred and therefore were able to compensate for the neurotoxic effect of the prenatal xylene exposure. Further studies are planned to investigate whether neurobehavioral effects resulting from prenatal xylene exposure can interact with neurophysiological aging processes.

Animals↗
PubMed1996

Trends in infectious diseases mortality in the United States.

OBJECTIVE: To evaluate recent trends in infectious diseases mortality in the United States. DESIGN: Descriptive study of infectious disease mortality, classifying International Classification of Diseases, Ninth Revision codes as infectious diseases, consequence of infectious diseases, or not infectious diseases. Multiple cause-of-death tapes from the National Center for Health Statistics for the years 1980 through 1992 were used, with a focus on underlying cause-of-death data and on codes that exclusively represent infectious diseases. SETTING: United States. SUBJECTS: All persons who died between 1980 and 1992. MAIN OUTCOME MEASURE: Death. RESULTS: Between 1980 and 1992, the death rate due to infectious diseases as the underlying cause of death increased 58%, from 41 to 65 deaths per 100,000 population in the United States. Age-adjusted mortality from infectious diseases increased 39% during the same period. Infectious diseases mortality increased 25% among those aged 65 years and older (from 271 to 338 per 100,000), and 6.3 times among 25- to 44-year-olds (from six to 38 deaths per 100,000). Mortality due to respiratory tract infections increased 20%, from 25 to 30 deaths per 100,000, deaths attributed to human immunodeficiency virus increased from virtually none to 13 per 100,000 in 1992, and the rate of death due to septicemia increased 83% from 4.2 to 7.7 per 100,000. CONCLUSIONS: Despite historical predictions that infectious diseases would wane in the United States, these data show that infectious diseases mortality in the United States has been increasing in recent years.

Adolescent↗
PubMed1996

Outbreak of vertigo in Wyoming: possible role of an enterovirus infection.

An epidemiologic investigation was conducted to characterize and evaluate the possibility of a viral aetiology of an outbreak of acute vertigo in Hot Springs Country, Wyoming, during autumn 1992. Case-finding identified Hot Springs County residents who sought medical attention for new onset vertigo during 1 August, 1992-31 January 1993. Thirty-five case-patients and 61 matched controls were interviewed and serum specimens were obtained during January 1993. Case-patients were more likely than controls to report symptoms (e.g. fatigue, sore throat, fever, diarrhoea) of antecedent acute illness. Case-patients did not have a significantly greater prevalence or mean titre of IgG antibodies to respiratory syncytial virus, parainfluenza viruses, Epstein-Barr virus, and cytomegalovirus than controls. Serologic evidence of recent enterovirus infection (IgM antibodies) was found for 74% of case-patients compared with 54% of controls (P < 0.05), suggesting a possible association between vertigo and enterovirus infection. Future studies are needed to define the role of enteroviruses in innerear diseases.

Adolescent↗
PubMed1996

Four weeks' inhalation exposure of rats to p-cymene affects regional and synaptosomal neurochemistry.

Long-lasting effects of inhalation exposure to p-cymene (p-isopropyl-toluene; CAS No. 99-87-6) on regional and subcellular brain neurochemistry were studied. Male Long-Evans rats were exposed to 0, 50, or 250 p.p.m. p-cymene 6 hr/day, 5 days/week for four weeks followed by an exposure-free period of 8 weeks. Synaptosomes were isolated from whole brain minus cerebellum and used as an ex situ model for in situ conditions at the level of the presynaptic nerve terminal. There was no persistent effect on wet weight (regional) or regional noradrenaline (NA), dopamine (DA), or 5-hydroxytryptamine (5-HT) concentrations owing to exposure. Yield of synaptosomal protein was statistically significantly reduced in an exposure concentration-related manner (Control: 16.6 +/- 3.1; 50 p.p.m.: 9.2 +/- 2.1; 250 p.p.m.: 8.6 +/- 1.7 mg protein/g tissue, mean +/- I.S.D.). Synaptosomal NA and DA concentrations and acethycholinesterase, butyrylcholinesterase, and lactate dehydrogenase activities were statistically significantly increased when expressed relative to synaptosomal protein. It is hypothesized that a reduced density and number of synapses in situ are functionally compensated for by increased NA and DA release from noradrenergic and dopaminergic presynaptic nerve terminals. The applicability of the synaptosome as an ex situ neurochemical research model for the presynaptic CNS nerve terminal in situ for the study of solvent neurotoxicity in rats was further supported.

Administration, Inhalation↗
PubMed1995

Multiple false reactions in viral antibody screening assays after influenza vaccination.

In December 1991, US blood centers reported an unusual increase in donations that tested falsely reactive for antibodies to two or more (multiple false positive) of the following viruses: human immunodeficiency virus type 1 (HIV-1), human T-cell lymphotrophic virus type I (HTLV-I), and hepatitis C virus. Many of these donations were from people who had recently received the 1991-1992 influenza vaccine, raising the possibility that this vaccine had somehow specifically caused the problem of multiple false reactivity. A case-control study of 101 affected donors and 191 matched controls found that recent receipt of any brand of influenza vaccine was significantly associated with testing multiple false positive (p < 0.05), as was a history of recent acute illness (p < 0.05) and of allergies (p < 0.05). Surveillance for monthly rates of multiple reactive donations from May 1990 through December 1992 linked the seasonal cluster of multiple false-positive donations to the use of viral screening test kits thought to react nonspecifically to donor immunoglobulin M. There was no similar increase in multiple false-positive donations during the 1992-1993 influenza vaccination season after the HIV-1 and hepatitis C virus tests were replaced; however, the number of donations that were falsely reactive for only HTLV-I almost doubled, indicating that false reactivity was not specifically associated with the 1991-1992 influenza vaccine. Retesting of affected donors found that the duration of HTLV-I and hepatitis C virus false reactivity was 3-6 months. The cluster of multiple false-positive donations in 1991 was most likely caused by the test kits used, rather than by the influenza vaccine.

Adolescent↗
PubMed1995

Glucose-induced thermogenesis in splanchnic and leg tissues in man.

1. Fourteen healthy subjects were investigated before and for 4 hours after oral intake of 75 g of glucose (n = 8) or tap water (n = 6). Whole-body energy expenditure was measured by an open-circuit ventilated hood system. Blood samples for determination of oxygen, carbon dioxide, glucose and lactate were taken from an artery, a hepatic vein and a femoral vein. Blood flow in the splanchnic region was measured by constant infusion of Indocyanine Green. Leg blood flow was measured by venous occlusion strain-gauge plethysmography. Oxygen uptake and carbon dioxide output in the splanchnic and leg tissues were calculated as the product of blood flow and arteriovenous differences in oxygen or carbon dioxide concentrations. Net exchanges of glucose and lactate across the splanchnic and leg tissues were calculated as the product of blood flow and arteriovenous differences in whole-blood glucose or lactate concentrations. 2. Splanchnic oxygen uptake had a biphasic course with an initial increase from 2.35 +/- 0.88 (SD) mmol/min to 2.85 +/- 1.20 mmol/min 30 min after the glucose intake (P < 0.005) and a later decrease below the basal value to around 2.02 mmol/min 90-180 min after the glucose intake (P < 0.05). The integrated increase in the splanchnic oxygen uptake during the 4 h after the glucose intake was -32.6 +/- 49.7 mmol/240 min. Leg oxygen uptake increased from 4.3 +/- 1.4 mumol min-1 100 g-1 to 7.0 +/- 3.2 mumol min-1 100 g-1 90 min after the glucose intake (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Evaluation of the magnitude of the 1993 hantavirus outbreak in the southwestern United States.

In May 1993, an outbreak of hantavirus pulmonary syndrome (HPS) in the southwestern United States was caused by the previously unrecognized Sin Nombre virus (SNV). Most HPS patients had an influenza-like prodrome, followed by rapid onset of pulmonary edema (fatality rate, 52%). To define the magnitude of the outbreak, patients with milder illnesses who sought medical care in the outbreak area during the outbreak period were assessed for infection with SNV. Of 299 study subjects, 43 had illnesses similar to the HPS prodrome. One laboratory finding, thrombocytopenia, was highly discriminatory between non-HPS patients (1%) and confirmed HPS patients (71%; P < .001) during the prodrome phase. No study subject had serologic evidence (IgM antibodies) of recent SNV infection. Five had IgG titers consistent with a previous hantavirus infection: 3 of these 5 were among the 43 patients who had illnesses similar to the HPS prodrome (P < .05). These data provide evidence that mild illness is rarely caused by SNV.

Adolescent↗
PubMed1995

Two weeks inhalation exposure to 4-tert-butyltoluene causes persistent changes in visually evoked potentials in rats.

The effects of repeated exposure to 20 p.p.m. 4-tert-butyltoluene (CAS No. [98-51-1]) 6 hr/day for 14 days on the function of the intact nervous system were examined by measurements of flash evoked potentials in Wistar rats. The exposure to 4-tert-butyltoluene induced changes in the amplitudes of the flash evoked potentials. The changes were significantly different from controls on day 2, 19 and 26 after cessation of the exposure, but not on day 5 and 12. No significant difference in body weight gain between groups was found during the experiment. These results indicate that repeated exposure to 20 p.p.m. 4-tert-butyltoluene causes persistent changes in the function of the central nervous system measured as changes in the flash evoked potential. A reevaluation of the present TLV value of 10 p.p.m. for 4-tert-butyltoluene is suggested.

Administration, Inhalation↗
PubMed1995

Four weeks inhalation exposure to n-heptane causes loss of auditory sensitivity in rats.

The effects of exposure to 800 or 4000 p.p.m. of n-heptane, CAS No. [142-82-5]) 6 hr per day during a period of 28 days, on the function of the auditory system were examined by measurements of auditory brain stem response (ABR) in Long Evans rats. The ABR was measured simultaneously with both needle electrodes and implanted electrodes. The wave forms recorded with the two types of electrodes were similar, but the amplitudes were largest on the recordings with implanted electrodes. The overall ratio between the amplitudes obtained with implanted electrodes and with needle electrodes was 1.4 for peak Ia and 2.5 for peak IV of the ABR. The exposure to n-heptane (4000 p.p.m.) reduced the amplitudes of components Ia and IV of the ABR. The reduction was most consistent for component IV and most pronounced at higher frequencies and intensities. The reduction in ABR corresponds to an increase in the auditory threshold of approximately 10 dB at all frequencies. Neither the latencies nor the interpeak latencies of components Ia and IV were changed. No significant changes in ABR were observed in the group exposed to 800 p.p.m. The mechanism behind the ototoxicity of organic solvents is discussed.

Administration, Inhalation↗
PubMed1995

Effect of training on epinephrine-stimulated lipolysis determined by microdialysis in human adipose tissue.

Trained humans (Tr) have a higher fat oxidation during submaximal physical work than sedentary humans (Sed). To investigate whether this reflects a higher adipose tissue lipolytic sensitivity to catecholamines, we infused epinephrine (0.3 nmol.kg-1.min-1) for 65 min in six athletes and six sedentary young men. Glycerol was measured in arterial blood, and intercellular glycerol concentrations in abdominal subcutaneous adipose tissue were measured by microdialysis. Adipose tissue blood flow was measured by 133Xe-washout technique. From these measurements adipose tissue lipolysis was calculated. During epinephrine infusion intercellular glycerol concentrations were lower, but adipose tissue blood flow was higher in trained compared with sedentary subjects (P < 0.05). Glycerol output from subcutaneous tissue (Tr: 604 +/- 322 nmol.100 g-1.min-1; Sed: 689 +/- 203; mean +/- SD) as well as arterial glycerol concentrations (Tr: 129 +/- 36 microM; Sed: 119 +/- 56) did not differ between groups. It is concluded that in intact subcutaneous adipose tissue epinephrine-stimulated blood flow is enhanced, whereas lipolytic sensitivity to epinephrine is the same in trained compared with untrained subjects.

3-Hydroxybutyric Acid↗